This invention relates to food mixing machines, and more particularly, to the access and chilling system for use in such machines.
Vacuum tumblers are large, cylindrical drums which are positioned with the cylinder access in a horizontal orientation or nearly horizontal orientation. Vacuum tumblers which are used to tumble massage meat, poultry and seafood products with a marinade are rotated about their axes. Integral with the tumbling process is the use of a vacuum to remove air in the meat and replace it with the associated marinade. Once the product is properly mixed, an additional and important use of the tumbler is to chill the product down to or near the freezing point of the meat cells in order to stiffen the meat so that it will retain a formed shape for cooking.
Vacuum tumblers of the type disclosed herein are similar to that disclosed in U.S. Pat. No. 5,104,232, which is assigned to the assignee of this invention. Such tumblers as described in the aforesaid patent may be designed with doors at one or both ends. The two-door version uses one of the doors for loading and the other for unloading. The one-door tumbler generally has a drum drive shaft welded or affixed at the end opposite the single door. The two-door tumbler is supported by drive wheels which rotate the drum by friction. Similar idler type wheels may be utilized in the axially driven drums in order to support the weight of the rotating drum.
A major use for vacuum tumblers is to chill the product for forming into shapes such as nuggets or patties before cooking. In order to make the meat stiff enough to form meat shapes out of small pieces of chicken, beef, or pork, it is necessary to chill down the meat so that thirty to forty percent of the meat cells are frozen. This is generally done by spraying a liquid cryogenic material such as liquid nitrogen or liquid carbon dioxide onto the meat. Utilizing this conventional system, the process chills down the drum, causing condensed water and frost to form on the outside of the drum. In the case of drive wheel drums, the slippery drum surface makes rotating the drum by friction very inefficient. Generally speaking, tumblers that are designed for chilling are direct-driven through a welded-on drive shaft and associated gearing or chain drive. These chilling tumblers are therefore restricted to having only one door.
In the one-door version, all the ingredients and additives must enter the single door to the vacuum tumbler through the door opening on the end opposite the tumbler drum drive shaft. In a large facility where meat is processed in batches of thousands of pounds, the single door type tumbler results in extreme congestion around the single door. This is caused because it is the only point at which product can be positioned in the tumbler. Carts or bins of product weighing between 400 pounds (180 kg) and 2,000 pounds (900 kg) must be lifted and poured or dumped into the tumbler drum through this single opening. The lift mechanisms, of course, are heavy and difficult to move.
The product must also be discharged through the same opening, up to 4,000 pounds (1800 kg) of product into the same 400 pound (180 kg) bins, one after another. With 30 inch (75 cm) diameter vacuum doors, the door is hinged and swung closed. Since the door is designed for a full vacuum, it is heavy and clumsy and requires a great deal of space to move into position.
At the same time, the tumbler must be provided with a means to inject liquid carbon dioxide or liquid nitrogen for chilling the product to make the formed shapes. This requires a second door to be moved into position. This door generally does not rotate with the drum as does the vacuum door as the stationary door not only contains the entry point for the liquid carbon dioxide or nitrogen, but it also contains a vent hose to vent away the cryogenic gas. Since the large vent hose must be permanently connected to the outside of the building, the vent door cannot rotate with the drum as does the vacuum door. This vent door is even more difficult to position than the vacuum door because the vent hose is attached. For cryogenic chilling, a long probe is attached to the door to reach into the drum so that nitrogen or carbon dioxide can be injected through the probe.
Nitrogen or carbon dioxide cryogenic flashes from a liquid into a gas very rapidly when it is sprayed into the atmosphere. Since the chilling efficiency is enhanced if the cryogenic nozzles are positioned close to the product during the injection and chilling processes, the probe should be long enough to reach the back of the drum where the product tumbles in the existing type drums, as disclosed in U.S. Pat. No. 5,104,232. In a production size tumbler, the nitrogen probe would have to be six to eight feet long, which is not practical since the probe must be removed after chilling each batch, two or three times per hour, to make room for connecting the vacuum door for the next batch. The longer the probe, the more difficult it is to keep it adjusted, the more room it takes up when it is retracted, and the more complicated the mechanism it requires to retract it. For these reasons, the probe has been designed quite short in existing production models, thereby reducing the efficiency of the cooling process.
One method that has been tried is to position the nitrogen injection probe on a track that moves in directly from in front of the door. In addition to being expensive, the probe mechanism takes up an enormous amount of valuable factory floor, not to mention the fact that the space is right in front of the loading and unloading area described above.
A second method is to rotate the nitrogen door and probe down from above the tumbler drum utilizing the head space above the machine. This solution improves the congestion in the critical area in the front of the door of the machine; however, the enormous mechanism required to rotate and position the probe system down from above the drum is very expensive and very difficult to keep in adjustment.
Both of the above systems result in poor efficiency and chilling with liquid nitrogen and carbon dioxide. Due to the need to keep the length of the probe short to minimize the retracted space problem, the spray nozzles end up too far from the product tumble zone. As a result, the majority of the cryogenic liquid flashes into gas rather than the droplets being sprayed onto the surface of pieces of the product and freezing onto the surface without flashing to gas.
When the cryogenic flashes to gas without making contact with the product, the gas freezes everything it contacts. The chilling efficiency is therefore reduced, creating a number of production problems, including freezing the stainless steel drum as well as the product pieces. In some instances, the product pieces will stick to the inside of the tumbler drum so that the stuck pieces remain in the drum after the product is discharged. To minimize the sticking problem, water is sprayed on the outside of the drum to keep the steel from reaching a temperature below freezing. The use of water in this way is expensive and messy, requiring expensive drainage systems and, in order to preclude wastage of water, a recirculating system. Since the purpose of the water spray is to heat up the tumbler drum to prevent it from freezing, more liquid nitrogen must be used to achieve the chilling. In those instances Where the chilling capacity of the liquid cryogenic is partially wasted on heating the steel drum by the water sprayed on the surface of the steel drum, substantially more cryogenic is required to chill the product. Since more cryogenic liquid is necessary and this liquid can only be sprayed on the product at a limited rate and still evenly coat the product pieces, it takes a longer time to chill the product. This reduces the utilization of the expensive machine, requiring more capital investment for more machines.
One of the problems with existing tumble mixers is associated with cleaning the interiors thereof. The vane system used to tumble the product is difficult to clean, with the back side of the vanes particularly hard to reach. Accordingly, in the larger tumble mixers, it is almost routine for an individual to climb inside the drum in order to perform a cleaning operation. Generally speaking, the individual carries therewith a hose or other cleaning material to accomplish the cleaning chore.
This invention overcomes the objections to the previous tumbler drums. In particular, it is an object of this invention to provide an axially-mounted, removable probe to provide material to the interior of a tumbler drum while the drum is rotating.
It is a further object of this invention to provide a probe system wherein a cryogenic liquid may be provided to the interior of a tumbler drum.
It is also an object of this invention to provide a probe system that may be used to provide product to be processed to the interior of a tumbler drum.
It is still another object of this invention to provide a probe system for a tumbler drum that can be used for cleaning.
It is also an object of this system to provide a probe system that can be utilized while the drum is rotating.
It is a further object of this invention to provide a probe system that is interchangeable so that a product supply probe can be replaced with a cryogenic probe, which in turn may be replaced with a cleaning probe.
Briefly stated, the invention comprises a tumble mixer having a rotatable drum with a horizontal axis. The rotatable drum includes a cylindrical midsection with an entry and discharge end section. The entry and discharge end section has an axial opening. The rotatable drum further includes a service access end section affixed to the rotatable drum at the end opposite the entry and discharge end section. Said service access end section is aligned axially with the rotatable drum axis. A material communication probe for providing material to the rotatable drum is also included. The service access end section defines an axially-aligned sealable entry for removably positioning the material communication probe within the cylindrical midsection whereby material can be communicated to the interior of the rotatable drum while the drum is rotating. Also included is the capability to rotate the drum by a drive member drivingly connected to the service access end.